The present invention relates to a gas wave-guide laser generator, comprising a resonant cavity with a wave-guide capillary, filled with a laser gas, and high-frequency electrical excitation or pumping means for provoking a discharge in the gas of the capillary.
Applications of such a generator are multiple and may for example be both medical and military.
Wave-guide capillary lasers already offer the advantage of a volumetric yield much greater than that of conventional lasers.
As to the high-frequency excitation process, for example in a frequency range of between 30 MHz and 3 GHz, preferably at 100 MHz, and which consists in creating an alternating electric field to induce a discharge in the gas, it also presents certain advantages per se.
The excitation voltage is low, for example 100 V, and precautions of insulation are no longer necessary.
The source of supply, or pumping, may be miniaturized.
The life duration is considerably increased due to the absence of anode and cathode for obtaining the discharge and therefore of drop in cathodic potential where the laser gas is dissociated.
The resonance cavity also serves as wave-guide for the energy generated.
It should be noted here that transverse excitation, i.e. the creation of an alternating electric field perpendicular to the longitudinal axis of the capillary is preferred to longitudinal excitation.
A wave-guide laser generator is already known, formed by two metal bars, or blocks, separated by two other dielectric bars, or blocks, or vice versa, the four of them forming, after assembly, a chamber or guide of rectangular cross section, the two metal bars serving as electrodes.
An insulating film may advantageously be applied on the inner wall of each of the metal bars to avoid oxidation thereof by the laser gas, the excitation field traversing this film.
A wave-guide laser generator is also known, of rectangular cross section, formed by a U-section closed by a cover plate, the section and the cover plate being made of alumina, and the electrodes, of thin metal layers, being applied on the walls of the cover plate and the section.
Although these two types of wave-guide lasers offer the advantages set forth hereinbelow, they nevertheless present certain drawbacks.
They are essentially limited to a wave-guide of square cross section.
Due to this geometry, there are several possible transverse modes translated by different aspects of the energetic distribution in the cross section of the laser beam, i.e. by spots.
In addition, the very structure of these lasers, whether they are of sandwich type or of cover plate type, leads to so-called assembled systems with four or two blocks, which present the drawbacks of the assembly.
From the optical standpoint, they generate deformations and therefore also optical losses.
From the industrial production point of view, they require an adjustment, soldering or gluing which can never be perfect.
Further, British Patent application No. 2 071 904 discloses a gas wave-guide laser generator incorporating a capillary, comprising a monolithic bar made of dielectric material, in which is formed a through capillary, a resonant cavity comprising the capillary, filled with the laser gas, and high-frequency electrical pumping means for provoking a laser discharge in the gas of the capillary.
Due to the monolithic character of the wave-guide, all the drawbacks associated with known gas tubes made by assembly are eliminated.
However, this latter generator comprises electrodes immersed in the capillary, so that they are oxidized by the laser gas which decomposes, this reducing the life duration of the laser. This phenomenon is also provoked by the electron bombardment (sputtering) of these electrodes, during the discharge.
It is an object of the present invention to eliminate these latter drawbacks.